Biosensors are commonly used to perform kinetic studies of complex molecular interactions such as those between drug-target, hormone-receptor, enzyme-substrate and antigen-antibody. The biosensors are typically in a flow injection-based fluidic system wherein one or more sensing regions are housed within a flow cell conduit of the fluidic system. The fluidic system further defines one or more flow channel conduits that direct fluid flow to the sensing regions in the flow cell conduit. The sensing region provides surfaces that support immobilized molecules referred to generally as “ligands.” The ligands are potential binding partners for molecules known as “analytes” which are present in fluids that are directed to the sensing region of the flow cell conduit via the flow channel conduit. Typically, one member of an affinity pair, the ligand, is immobilized onto a surface in the sensing region while the second member, the analyte, is exposed to this ligand-coated surface for sufficient time to form analyte-ligand complexes at the sensing region.
Competition assays provide the ability to find active site binders directly by competing fragment hits with a control molecule. Such assays are commonly performed using surface plasmon resonance (SPR). However, competition assays typically require multiple steps in order to determine full kinetic and affinity data for the competing molecules. As a result analysis is time consuming and costly.